How about the Karma? It is readily available for $1799. While not a conventional arranger, it does provide great autoaccompaniment. The Karma excels at ethnic music, coming with factory African, Latin, Indian, Indonesian (Gamelan), and Japanese autoaccompaniments. The Karma comes with the Triton sound engine. Both the sounds and the accompaniment can be tweaked in real time. Both the Triton engine and the Karma engine can be edited to create new sounds. (One of the little-recognized functions of the Karma architecture is the generation of Wavesequence-like sounds.)
The Karma accepts the MOSS option (much beter than the Yamaha VL and AN options) for great virtual acoustic and virtual analog sounds. In addition, there is room for two 16MB sound ROM expansions. Adding any of these options brings the price to above $2000, but you do not have to buy them up front.
The Karma does not come with vocal harmony, which I feel is unfortunate. However, you can add an outboard vocal harmonizer, like the VoicePrism. The external vocal harmonizer can then be controlled by the Karma function for some intriguing possibilities.